The Christian Left refers to a number of contemporary left-wing political movements that are specifically Christian, that push progressive ideas in politics and the popular culture. While the Christian Right has been more visible in recent politics, a number of Christian Left organizations, or their predecessors, have long histories. There was a strong religious position against slavery, for example, before the American Civil War.
In current political interaction, it is a mistake to equate all American religious views as evangelical, social conservative, and Republican, just as much as it would be incorrect to assume that there are no religious effects, in the public square, which come from people who are not Christian at all, and possibly not of Abrahamic faiths. Indeed, not all evangelicals are Republican. "Freestyle evangelicals", in the words of the liberal journal American Prospect, have
concerns extend beyond the conservative morality issues of abortion and gay marriage to progressive matters of social justice, America's role in the world, and care for the environment. The sociologist Stephen Hart describes Christian faith as comprising a set of elemental moral "building blocks" that believers "assemble" in countless combinations to construct their social ethics. Freestyle evangelicals have neither an exclusively Democratic nor Republican worldview; they say they often find themselves in the tiresome position of electing officials who will do the least amount of damage rather than the most good. As one believer told the Prospect, "I am a political moderate, not despite my theological conservatism but because of it." 
Historically, non-evangelical Christians in American politics go back to the Quakers in colonial and early days of the U.S. as a nation. Roman Catholics also had strong social views, although they were not the core of American Christianity. Catholic conflict included issues of mixed loyalties to the Catholic hierarchy in the 1960 United States presidential election, from which John F. Kennedy became the first Catholic President.
Other socially active spiritual groups, such as Unitarian Universalism, do not consider themselves Christian but frequently find common ethical principles.
One categorization breaks the religious left into four parts: While the religious left generally shares a disgust with the religious right and the secular left, in many ways they are not entirely unified. Here's a primer on the key factions.
- Bible-thumping liberals: "Many Democrats consider the term "progressive evangelical" to be an oxymoron. Between 7 and 10 percent of the electorate are white evangelical Christians who either vote Democratic or could. That's a voting bloc equal in size to African-Americans. Instead, evangelicals break into three groups:
- Fundamentalists (think Jerry Falwell, Pat Robertson, James Dobson) are solidly Republican and represent about 15 percent of the electorate.
- Moderates represent another 9 percent. They generally voted for Bush because they agreed with him on foreign policy and abortion and same-sex marriage; those for whom economics was the most important issue voted for John Kerry.
- Liberal evangelicals, who make up about 3 percent of the electorate and tend to vote Democratic; they are most concerned about poverty and environmentalism. Their most important leaders are Jim Wallis and Tony Campolo, who suport politicians who cast their policies in religious terms—for instance, by reminding us that the Bible urges a fight against poverty. As Wallis wrote, "[M]any of the most progressive social movements in American history—anti-slavery, women's suffrage, the fight for child labor laws and the civil rights movement—had overt religious roots and motivations."
- Pious peaceniks: This group is in the tradition of the spirit of the anti-war movement of the 1960s and 1970s and the nuclear freeze movement of the 1980s. They have mobilized in opposition to the Iraq war and have a strong interest in environmentalism and antagonism toward corporate America. Exemplars are Cindy Sheehan, the National Council of Churches, the Roman Catholic Church, Faithful America, and the Christian peacemakers who camped out in Iraq as human shields. "Unlike the Bible-thumpers, they tend to align almost down the line with secular liberals, disliking Clinton's New Democrat philosophy, especially its emphasis on welfare reform and crime fighting, which they thought demonized the poor and minorities. With respect to abortion, they are silent or pro-choice.
- Ethnic churchgoers: In this group are African-Americans, Hispanics, and Muslims, who together accounted for about 19 percent of the Kerry vote in 2004. They often like Republican values on social issues but look to Democrats to defend their civil rights. Though they also opposed the Iraq war and share the views of other religious lefties about the importance of fighting poverty and protecting the environment, they differ from the other groups on abortion and, even more so, gay rights. Muslims may have supported George W. Bush in 2000 because they agreed with his social conservatism, but switched to the Democrats in 2004 because of the Patriot Act.
- Conflicted Catholics: "Liberal Catholics are like liberal Protestants and Jews on poverty, war, and the environment. Slight differences arise around gay marriage and abortion. Though more pro-choice than Hispanics or blacks, liberal Catholics tend to feel guiltier about abortion. The real difference may not be in the policies they support—the majority want abortions to be legal but restricted, just like the majority of the rest of the population—but in their attitudes toward pro-life people. Liberal Catholics are less likely than secular liberals to hold pro-lifers in contempt. To frame abortion for this group, Democrats at least need to pretend that they want to reduce the number of abortions. And even as they fight to keep abortion legal, the Dems shouldn't mock pro-life advocates as sexually repressed theocrats or describe abortion as merely a surgical procedure."
- Religious feminists: This is perhaps the newest faction. In aiming to win for women the right to control their own bodies, feminism ran up against the patriarchy of many religious institutions. Some feminists, however see spirituality as an important part of their lives and have begun trying to bring faith into their movement.
Family and relationships
There may be some issue overlap with the Christian Right, but usually a different approach. For example, both believe in the value of family. Left groups, however, often are accepting of committed gay and lesbian relationships. Where both discourage abortion, the left groups are more apt to support birth control and have strong interest in child welfare beyond pregnancy and birth.
Science and religion
While some matters are indeed considered in the realm of faith, in general, scientific approaches are more mainstream in the Christian Left than the Christian Right. Speaking of his personal path, Francis Collins, Director of the National Institutes of Health in the Obama Administration, said
I became an atheist and held that view as a graduate student in chemistry. It was only when I went to medical school and faced up to life and death issues that were surrounding me in hospitals and clinics that I realized my atheism had been arrived at pretty much because it was the answer I wanted, not because I’d really looked at the evidence. I realized that if I was facing death, I would be terrified. I needed to understand what the faith issues were that seemed to be such a comfort to so many of my patients. I began to pursue whether there is a rational basis for faith. I assumed there wasn’t and that this was all about emotion and some sort of vague spiritual experience. I was surprised to learn that in fact there is a very strong rational case to be made for belief in God. I encountered that particularly in the writings of C.S. Lewis." As opposed to faith being an major part of biomedical confirmation hearings in the previous administration, he says "I have no religious agenda for the NIH. In fact, it would be utterly inappropriate for me to impose my spiritual beliefs on this scientific agency. But for myself, I will certainly be depending on my faith for encouragement and strength, as I face the many storms that no doubt lie ahead in such a visible and complex professional position." 
Not an uncommon practice, Collins regards religion as separate from science, but strongly tied to ethics in the application of science.
According to a Wall Street Journal article, political consultants have been barraged with calls from business interests in the southern United States,concerned with a "massive ad blitz on Christian and country-music stations across 10 states. The ads, funded by a left-leaning coalition, urge support for congressional legislation to curb greenhouse-gas emissions -- by framing the issue as an urgent matter of Biblical morality." 
A coalition including Faith in Public Life, Sojourners and Catholics in Alliance for the Common Goodis distributing an eight-page guide, full of Biblical quotes and health-care statistics, to encourage pastors to raise environmental issues. "Democratic lawmakers representing conservative districts say such efforts help them make the case to skeptical constituents that they aren't simply toeing the party line -- or turning into bleeding-heart liberals -- when they support President Barack Obama's calls for health-care and climate-change legislation. "It's important for people to see that it's not just [Democrats] saying this is important, but people who are coming at it from a moral background,"" said Rep. Tom Perriello (D-Virginia), a freshman Democrat who has come under fire in his rural district for supporting the climate bill."
Their approach to valuing human life usually implies opposition to capital punishment, and, depending on the group, attitudes ranging from great reluctance to use military force, to complete pacifism. Sojourners, for example, starts with a value position that "All life is a sacred gift from God, and public policies should reflect a consistent ethic of life."
During the Vietnam War, religious groups and individuals were prominent in objecting to the war on religious reasons. Jesuit Fathers Daniel and Phillip Berrigan, for example, were among the "Catonsvile Nine" who destroyed draft records in 1968. They served jail terms.
Health care reform is a major current issue in American politics. In August 2009, a coalition of Christian Left groups started a “40 Days for Health Reform” initiative, with a national television advertisement, prayer events, and a national sermon weekend. Rev. Stevie Wakes, a Baptist minister participating in the program, contrasted the Christian Left view that providing health care was a moral imperative, with the Christian Right position that abortion was the central issue. He cited a Family Research Council advertisement showing "an elderly man and his wife are shown sitting at their kitchen table talking about how the government won’t pay for the man’s surgery but forces them to pay for abortions – a reference to the “abortion mandates” that have been strongly contested by members of the pro-life community" The campaign was led by PICO National Network, Faith in Public Life, Faithful America, Sojourners, and Catholics in Alliance for the Common Good. The opening of the 40 days was led by Rev. Adam Hamilton of theChurch of the Resurrection, Leawood, Kan. Rabbi David Saperstein, director of the Religious Action Center of Reform Judaism.
There is actually some agreement, among elements of the Christian Right and Left, that at least elective abortions should not receive public funding, but the Left generally sees overall health care as a more critical imperative.
In this intense battlefield of the culture wars, a group such as Sojourners has the goal
Dramatically reduce abortion. Our society should support common ground policies that dramatically reduce the abortion rate by preventing unwanted pregnancies, providing meaningful alternatives and necessary supports for women and children, and reforming adoption laws.
- "Reaching to the Choir", American Prospect, 23 March 2004
- Steven Waldman (5 April), The Religious Left: It is fruitful and has multiplied.
- Jeannie Choi (February 2010), "Interpreting the Language of God", Sojourners Magazine
- Stephanie Simon (3 July 2009), "In Political Ads, Christian Left Mounts Sermonic Campaigns", Wall Street Journal
- Frequently Asked Questions on the Issues, Sojourners
- Chris Hedges (20 May 2008), "Daniel Berrigan: Forty Years After Catonsville", The Nation
- "'Religious Left' to Launch Pro-Health Care Reform Campaign", Christian Post, 10 August 2009